High-glycemic index carbs may cause excess hunger

A study published in the American Journal of Clinical Nutrition shows that consuming highly processed carbohydrates may cause excess hunger and stimulate brain regions involved in reward and cravings.

The researchers measured blood glucose levels and hunger, while also using functional magnetic resonance imaging (MRI) to observe brain activity during the crucial 4-hr period after a meal, which influences eating behavior at the next meal. Evaluating patients in this time frame is one novel aspect of this study, whereas previous studies have evaluated patients with an MRI soon after eating.

Twelve overweight or obese men consumed test meals designed as milkshakes with the same calories, taste, and sweetness. The two milkshakes were essentially the same; the only difference was that one contained rapidly digesting (high-glycemic index) carbohydrates and the other slowly digesting (low-glycemic index) carbohydrates.

The researchers found that after participants consumed the high-glycemic index milkshake, they experienced an initial surge in blood sugar levels, followed by sharp crash 4 hrs later. This decrease in blood glucose was associated with excessive hunger and intense activation of the nucleus accumbens, a critical brain region involved in addictive behaviors.

“These findings suggest that limiting high-glycemic index carbohydrates like white bread and potatoes could help obese individuals reduce cravings and control the urge to overeat,” said David Ludwig, Director, New Balance Foundation Obesity Prevention Center, Boston Children's Hospital.